Background: Cryptosporidiosis is an important cause of diarrhea in children and immunosuppressive patients. The current study was intended to evaluate the prevalence rate of Cryptosporidium infection and clarify the epidemiological characteristics of the infection in both children and immunosuppressive patients in Iran.Methods: Five English electronic databases including PubMed, Google Scholar, Science Direct, Scopus and Cochrane, and two Persian language databases Magiran and Scientific Information Database were searched. Additionally, reports from the Iranian congresses of parasitology and graduate student thesis dissertations were assessed manually.Results: Out of 1856 studies from the literature search, our search resulted in a total of 27 articles published from 1991 to 2016. These include 14 reports on cryptosporidiosis in children and 13 papers regarding immunosuppressive patients. 8520 children and 2015 immunosuppressed cases were evaluated. Oocysts of Cryptosporidium were found in 3.8% and 8% children cases and immunosuppressed patients, respectively. There was a relatively high variation in the prevalence estimates among different studies, and the Q statistics was high among articles regarding children (p<0.0001) and also between records regarding immunosuppressed patients (p<0.0001). Findings showed that the prevalence rates of Cryptosporidium infection are significantly higher in children under 5 years (P=0.00).Conclusions: In summary, the present study provides a comprehensive view of the epidemiology of Cryptosporidium in children and immunosuppressive patients in Iran. Furthermore, a multidisciplinary and multicenter study to evaluate the real prevalence of Cryptosporidium infection and to determine its risk factors using an adequate sample size and standardized methods is highly recommended.